In the field of high-end optics, the demand for fluorescent-tunable polymers is increasingly urgent. However, traditional fluorescent materials have limitations including insufficient stability, poor processability, and volatile organic compound (VOC) pollution. In this study, using an improved acetone method synthesis process, Schiff base Cu(II) complexes were innovatively introduced into the main chain of waterborne polyurethane (WPU), to successfully prepare fluorescencecontrollable PMBxCu1-WPU (x = 1, 2, 3), realizing the stable bonding of the Schiff base ligand (PMB) and Cu(II) in the polyurethane chain. The successful synthesis of PMB and the structure of the PMBxCu1-WPU were confirmed by nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, X-ray powder diffractometer and other testing methods. It was found that the particle size of PMBxCu1-WPU increased by increasing Cu(II) content, and the absolute value of its Zeta potential exceeded 40 mV, showing excellent dispersion stability. PMBxCu1-WPU still maintained good thermal stability, with an initial decomposition temperature of about 220 °C. With the increase in Cu(II) coordination degree, the UV-vis absorption peak undergoes a certain degree of redshift. It is worth noting that after PMB was incorporated into WPU, its emission peak redshifted from 499 nm to 551 nm; with the increase of Cu(II) coordination degree, the emission peak further blue-shifted to 534 nm, which indicates that the fluorescence emission wavelength of PMBxCu1-WPU can be precisely regulated by the coordination degree of Cu(II). This study provides a new method for developing high-performance fluorescent-tunable waterborne polyurethane, and has potential application in the fields of intelligent anti-counterfeiting and biomedicine.

Abstract
1. Introduction
2. Experimental Procedure
    2.1. Materials
    2.2. Preparation
    2.3. Sample Preparation and Testing Methods
3. Results and Discussion
    3.1. NMR and FT-IR of PMB
    3.2. FT-IR Spectra of WPU, PMB-WPU and PMBxCu1-WPU
    3.3. XRD Analyses
    3.4. Emulsion Particle Size and Zeta PotentialAnalysis
    3.5. TG-DTG of WPU, PMB-WPU and PMBxCu1-WPU
    3.6. UV-Vis Spectra of PMB, WPU, PMB-WPU andPMBxCu1-WPU
    3.7. Fluorescence Spectroscopy of PMB, WPUand PMBxCu1-WPU
4. Conclusion
Acknowledgement
References
Author Information

• Xin Bu(Reheo Technology Co., Ltd., Hefei 230088, China)
• Tianfu Wang(Reheo Technology Co., Ltd., Hefei 230088, China)
• Kaixuan Shao(Anhui Key Laboratory of Advanced Building Materials, School of Materials Science and Chemical Engineering, Anhui Jianzhu University, Hefei 230601, China)
• Kehua Zhang(Anhui Key Laboratory of Advanced Building Materials, School of Materials Science and Chemical Engineering, Anhui Jianzhu University, Hefei 230601, China) Corresponding author
• Mingdi Yang(Anhui Key Laboratory of Advanced Building Materials, School of Materials Science and Chemical Engineering, Anhui Jianzhu University, Hefei 230601, China)
• Xianhai Hu(Anhui Key Laboratory of Advanced Building Materials, School of Materials Science and Chemical Engineering, Anhui Jianzhu University, Hefei 230601, China) Corresponding author